Stampings

Reinforced TS plastic B-stage sheet material can be used with its required heating cycle (Chapter 3). However, the most popular is to use TP sheets. 

Different forms of glass fiber/TS plastics are used with or without special surface coatings such as gel coatings. Materials are compounded with controlled pot life so that they start their cure reaction after being placed in the mold cavity. For room temperature cure, cure occurs by an exothermic chemical reaction that heats the RP. Pressures are moderate at about 20 to 50 psi (140 to 350 kPa). Molds can be made of inexpensive metal, plaster, RP, wood, etc. 

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It is applied along with traditional methods to test strength properties, hardness, to determine standardized characteristics of stamping, grain size and other structural-sensitive characteristics. 

This German stamp depicts a molecular model of urea and was issued in 1982 to commemorate the bun dredth anniversary of Woh ler s death The computer graphic that opened this in troductory chapter is also a model of urea... 

A 1968 German stamp com bines a drawing of the struc ture of benzene with a portrait of Kekule... 

Linus Pauling is portrayed on this 1977 Volta stamp The chemical formulas depict the two resonance forms of ben zene and the explosion in the background symbolizes Pauling s efforts to limit the testing of nuclear weapons... 

The discoverer of penicillin Sir Alexander Fleming has appeared on two stamps This 1981 Hungarian issue includes both a likeness of Fleming and a structural for mula for penicillin... 

Many countries have cele brated their chemical indus try on postage stamps The stamp shown was issued in 1971 by Argentina... 

A DNA double helix as pic tured on a 1964 postage stamp issued by Israel... 

Pages 2,3, 4,5 Stamps are courtesy of James O Schreck Professor of Chemistry University of Northern Colorado... 

In manufacture, the abrasive grain is mixed with cmde mbber, sulfur, and other ingredients for curing, then passed through calender roUs to produce a sheet of desired thickness. The wheels are stamped from this sheet and heated under pressure to vulcanise the mbber. 

ICIFM-21SP Monopolar Electrolyzers. Id s EM-21 SP monopolar electrolyzer incorporates stamped electrodes that are 2 mm thick and of a relatively small (0.2 m ) size (50). The electrolyte compartments are created by molded gaskets between two of the electrode plates the electrode spacing is finite and is estabHshed by gasket thickness. The electrode frames are supported from rails and are compressed between one fixed and one floating end plate by tie rods. Inlet and outlet streams are handled by internal manifolds. A crosscut view of the electrolyzer is shown in Eigure 21. As of 1989, ICI had Hcensed 20 plants having an annual capacity of 468,250 t of NaOH. 

Injection-molded articles can be decorated by in-mold labeling or by post-mold decoration. In the former method, printed film is inserted into the mold cavity before injection. The plastic forms an intimate contact with the graphic material. Post-mold decoration includes hot stamping, dry offset printing, and decal printing. 

CD-ROM disks are nearly identical to the weU-known compact disk-digital audio (CD-DA short CD). The information on a CD-ROM is stamped in the form of clearly defined pits on the disk surface during the disk s manufacture, using injection mol ding or injection stamping techniques. A metal stamper transfers the digital information to the disk s surface. 

The birefringence for phenyl-substituted PC (4) (T = 176 C) is reduced to about 50%, for benzyl substituted PC (5) (T = 138 C) to about 25%, and for four-ring bisphenol PC (6) to 8% of the value for BPA-PC (183,190,195,197,198) on condition of an optimum conformation of the phenyls in the side groups perpendicular to the aromatic rings in the backbone. In reaUty, however, these low birefringence values are not achieved, because the optimum conformation of the phenyl rings cannot be achieved in injection-stamped disks. 

Stamp-Pad Inks. These inks are impregnated into a cloth or foam mbber pad and transferred by pressure to mbber type which is then stamped or impressed against the substrate. The inks must be completely nondrying in the pad and yet dry by rapid penetration into the paper. Since it is desirable that the total ink soak into the stock, dyes are used rather than pigments. The vehicles used are usually glycols. 

Fig. 13. Various forming operations (a) backward extmsion (b) deep drawing (c) spinning (d) bending (e) stretching (f) stamping (g) coining (h)...

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